Such an optical measuring device is discussed in German Published Patent Application No. 198 08 273. In this measuring device including a fiber-optic, temporarily coherent multiple wavelength heterodyne interferometer as a part, a measuring probe to be aligned toward the object surface and a reference probe to be aligned toward a measuring table on which the object or component including the surface is located are connected to a beam inlet section including a temporarily coherent broadband light source and a modulation interferometer that absorbs this light. As discussed in German Published Patent Application No. 198 08 273, this configuration of the measuring device including a broadband light source that is rather unusual for the heterodyne method and may allow for a coherence multiplex in that, in a modulation interferometer, e.g. including the more complex components and optical configurations, the different interferometer arms are used to imprint different optical path lengths that are greater than the coherence lengths of the radiation passing through them and that are subsequently balanced again in a measuring section via the optical probe configuration so that the interference instances occurring only within the coherence length are obtained and the surface regions are able to be determined on the basis of the phase differences in the connected evaluation device.
The individual wavelengths for the heterodyne technique or the heterodyne method may also be easily and suitably extracted via a beam splitting and beam receiving unit from the (relatively) broadband radiation spectrum so that the region of clarity of the distance or roughness measurement is able to be enlarged with respect to the individual wavelengths by forming one or more synthetic wavelengths. Due to further advantages of the configuration of such a multiple wavelength heterodyne interferometer including a modulation interferometer, reference is made to further exemplary embodiments in this document. However, in practice, demands may result that require a relatively significant expenditure even for such a measuring device, for example when different surfaces or surface regions are to be measured with respect to different geometric data. In this case, the adjustment work may prove to be difficult, and configuration may prove to be expensive due to the adjustment to the different measuring tasks.
In addition to punctual measuring interferometric measuring devices of the abovementioned type, areal measuring interferometric measuring devices may also be available that are based on white-light interferometry or interferometry using temporarily coherent radiation and that may allow precise determination of the form and roughness of functionally relevant surfaces, e.g. in the automobile industry. Such white-light interferometers are explained in further detail for example in T. Dresel, G. Haeusler, H. Venzke, “Three-dimensional sensing of rough surfaces by coherence radar”, Appl. Opt. 31, 919 (1992) as well as in P. de Groot and L. Deck, “Surface profiling by analysis of white-light interferograms in the spatial frequency domain”, Journal of Modern Optics, Vol. 42, 389-401 (1995).
Areal-ly measuring white-light interferometric methods are characterized by the fact that a complete section of the functional surface is recorded during a measuring operation via an areal image recorder. The information density is high and may allow a plurality of form and surface parameters to be determined in this section. Various modifications of this have already been developed, e.g. using an endoscope to measure in deep bore holes as in German Patent Application No. 199 48 813 and German Patent Application No. 100 15 878, optics to generate wave fronts adapted to special geometries, such as panoramic optics as in German Patent Application No. 100 39 239.
Punctual measuring interferometric methods are characterized by the fact that the object surface is scanned by a probe scanning in a measuring point successively along a predefined path. In general, this is performed with the help of a highly precise mechanical form measuring machine that guides the test part along the probe or the probe along the test part. As shown by the use of a single fiber, as in German Patent Application No. 100 57 539, probes may be produced with extremely small diameters.
Punctual and areal measuring interferometric methods may provide advantages with respect to the recording of technically relevant measuring features. For example, to measure concentricity of a valve seat to a guide bore in a motor, a punctual measurement is performed, while an areal method is used for a radius determination or a bur detection at a spray hole inlet.